lkml.org 
[lkml]   [2020]   [Sep]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH 3/6] seccomp: Implement constant action bitmaps
Date
From: Jann Horn
> Sent: 24 September 2020 13:29
...
> I think our goal here should be that if a syscall is always allowed,
> seccomp should execute the smallest amount of instructions we can get
> away with, and touch the smallest amount of memory possible (and
> preferably that memory should be shared between threads). The bitmap
> fastpath should probably also avoid populate_seccomp_data().

If most syscalls are expected to be allowed then an initial:
if (global_mask & (1u << (syscall_number & 63))
test can be used to skip any further lookups.

Although ISTR someone suggesting that the global_mask should
be per-cpu because even shared read-only cache lines were
expensive on some architecture.

David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
\
 
 \ /
  Last update: 2020-09-24 14:38    [W:0.137 / U:4.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site